--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/Wzero-length-array-bounds-2.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,125 @@
+/* Test to verify that -Wzero-length-bounds and not -Warray-bounds is
+   issued for accesses to interior zero-length array members that are
+   within the bounds of the enclosing struct.
+   { dg-do compile }
+   { dg-options "-O2 -Wall" } */
+
+void sink (void*);
+
+struct A { int i; };
+struct B { int j; struct A a[0]; };
+
+struct C
+{
+  struct B b1;
+  struct B b2;
+};
+
+
+void test_B_ref (struct B *p)
+{
+  // References with negative indices are always diagnosed by -Warray-bounds
+  // even though they could be considered the same as past the end accesses
+  // to trailing zero-length arrays.
+  p->a[-1].i = 0;       // { dg-warning "\\\[-Warray-bounds" }
+  p->a[ 0].i = 0;
+  p->a[ 1].i = 0;
+  sink (p);
+
+  p[1].a[-1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  p[1].a[ 0].i = 0;
+  p[1].a[ 1].i = 0;
+}
+
+
+void test_C_ref (struct C *p)
+{
+  p->b1.a[-1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b1.a[ 0].i = 0;     // { dg-warning "\\\[-Wzero-length-bounds" }
+  p->b1.a[ 1].i = 0;     // { dg-warning "\\\[-Wzero-length-bounds" }
+
+  // Accesses to trailing zero-length arrays are not diagnosed (should
+  // they be?)
+  p->b2.a[ 0].i = 0;
+  p->b2.a[ 9].i = 0;
+}
+
+
+void test_C_decl (void)
+{
+  struct C c, *p = &c;
+
+  p->b1.a[-1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+
+  // c.b1.a[0].i overlaps c.b2.j.
+  p->b1.a[ 0].i = 0;     // { dg-warning "\\\[-Wzero-length-bounds" }
+
+  // c.b1.a[1].i is past the end of c...
+  p->b1.a[ 1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+
+  // ...and so are references to all elements of c.b2.a
+  p->b2.a[ 0].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b2.a[ 1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+}
+
+
+char cbuf1[1 * sizeof (struct C)];
+char cbuf2[2 * sizeof (struct C)] = { };
+
+void test_C_global_buf (void)
+{
+  struct C *p = (struct C*)&cbuf1;
+
+  p->b1.a[-1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b1.a[ 0].i = 0;     // { dg-warning "\\\[-Wzero-length-bounds" }
+  p->b1.a[ 1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+
+  p->b2.a[ 0].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b2.a[ 1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+
+  p = (struct C*)&cbuf2;
+  p->b1.a[-1].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b1.a[ 0].i = 0;     // { dg-warning "\\\[-Wzero-length-bounds" }
+  p->b1.a[ 1].i = 0;     // { dg-warning "\\\[-Wzero-length-bounds" }
+  sink (p);
+
+  p->b2.a[ 0].i = 0;
+  p->b2.a[ 1].i = 0;
+  p->b2.a[ 2].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b2.a[ 3].i = 0;     // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+}
+
+
+void test_C_local_buf (void)
+{
+  char cbuf1[1 * sizeof (struct C)] = "";
+  char cbuf2[2 * sizeof (struct C)] = { };
+
+  struct C *p = (struct C*)&cbuf1;
+
+  p->b1.a[-1].i = 1;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b1.a[ 0].i = 2;     // { dg-warning "\\\[-Wzero-length-bounds" }
+  p->b1.a[ 1].i = 3;     // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+
+  p->b2.a[ 0].i = 4;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b2.a[ 1].i = 5;     // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+
+  p = (struct C*)&cbuf2;
+  p->b1.a[-1].i = 6;     // { dg-warning "\\\[-Warray-bounds" }
+  p->b1.a[ 0].i = 7;     // { dg-warning "\\\[-Wzero-length-bounds" }
+  p->b1.a[ 1].i = 8;     // { dg-warning "\\\[-Wzero-length-bounds" }
+  sink (p);
+
+  p->b2.a[ 0].i = 9;
+  p->b2.a[ 1].i = 10;
+  p->b2.a[ 2].i = 11;    // { dg-warning "\\\[-Warray-bounds" }
+  p->b2.a[ 3].i = 12;    // { dg-warning "\\\[-Warray-bounds" }
+  sink (p);
+}